Comparison of physiological and biochemical methods for assessing microbial activity and biomass of peats

Abstract

Physiological and biochemical methods developed to measure microbial activity and biomass in mineral soils may not give reliable results in highly organic potting media used in horticulture (e.g. peats). In this study, the suitability of the substrate-induced respiration (SIR), fumigation incubation (FI), fumigation extraction (FE), arginine ammonification (AA) and N-stability methods to measure microbial activity and biomass in peats were evaluated. These peats (n = 20) were obtained from different bogs and fens of Estonia, Finland, Germany, Ireland, Latvia, Lithuania and Sweden. Basal respiration (24 to 128 CO2-Cg-1 dry peat d-1) was greatly influenced by the total-C (r = -0.66), C/P (r = -0.62), and N/P (r = -0.67) ratio. However, it correlated poorly with the total-N (r = -0.14), pH (r = -0.15), organic matter content (r = 0.01), and the C/N ratio (r = -0.06) indicating that microbial activity in Sphagnum dominated peats cannot be predicted from these variables. Microbial biomass-C estimated by the SIR (MB-CSIR) and the FE (MB-CFE) methods ranged from 276 to 1802 μg Cg-1 dry peat and from 397 to 2172 μg C g-1 dry peat, respectively. Basal respiration showed strong correlations with MB-CSIR (r = 0.89) and MB-CFE (r = 0.83) methods. The equation: MB-C = 2.372 ± 0.059 (extractable C-flush; EC) also gave an overall proportionality factor (kEC) of 0.422, which is nearly similar to the mean value of individual kEC computed as the ratio of EC to MB-CSIR (0.436 ± 0.09) to suggest that FE and SIR are the reliable methods to estimate microbial biomass in a wide range of peat samples. Evolution of CO2-C from the fumigated peat samples was slightly higher than the corresponding unfumigated samples suggesting that mineralization of dead microbial biomass-C over 10 d was poor in the tested peat samples. However, all peat samples rendered positive flush-C when evolved CO2-C from the unfumigated peat sample (measured between day 10 and 20) was used as a respective control treatment. Overall, microbial biomass estimated by the FI method (170 to 2411 μg g-1 dry peat), liberated ammonium from added arginine (18 to 76 μg g-1 dry peat h-1) and mineral-N changes over two weeks (-6.1 to -124.5 mg N L-1) correlated poorly with the microbiological and physicochemical data. ©2012 Nova Science Publishers, Inc.

Keywords

Arginine ammonification; Basal respiration; Fumigation extraction; Fumigation incubation; N-stability test; Peat; Substrate-induced respiration

Published in

Title: Peat : Formation, Uses and Biological Effects
Publisher: Nova Science Publishers

SLU Authors

• Alsanius, Beatrix

  • Horticulture, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Agricultural Science

Publication identifier

• ISBN: 978-1-62100-162-1
• eISBN: 978‐1‐62100‐198‐0

Permanent link to this page (URI)

https://res.slu.se/id/publ/132241